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RSS2014 Vol. 38, No. 5
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2014, 38(5): 579-585.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.001
[Abstract]
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Abstract:
In order to study coupled optoelectronic oscillators (COEO) further, the mode selection theory of COEO was expounded. The phase matching condition to maintain optimum mode-locked state was given. The affecting factors of phase noise of radio frequency signal were analyzed. The experiment of COEO based on polarization-maintaining mechanism was conducted. By adjusting the polarization-maintaining variable optical fiber delay lines in the optical ring cavity and the optoelectric microwave oscillation loop to change the cavity length, the relationship between cavity length and oscillation frequency was obtained. Meanwhile, by using the frequency discrimination method, phase noise performances of 5GHz radio frequency(RF) signals under different operating conditions were measured and the effective factors were studied. The experimental results demonstrate that oscillation mode depends on the cavity length of optical ring cavity. Optical signal polarization, phase matching and loop length have influence on the phase noise of the RF signals. The coupled optoelectronic oscillator of 5GHz RF signal and phase noises of -136dBc/Hz at 10kHz offset frequency is obtained, whose phase noise is the lowest in our country as far as we know.
In order to study coupled optoelectronic oscillators (COEO) further, the mode selection theory of COEO was expounded. The phase matching condition to maintain optimum mode-locked state was given. The affecting factors of phase noise of radio frequency signal were analyzed. The experiment of COEO based on polarization-maintaining mechanism was conducted. By adjusting the polarization-maintaining variable optical fiber delay lines in the optical ring cavity and the optoelectric microwave oscillation loop to change the cavity length, the relationship between cavity length and oscillation frequency was obtained. Meanwhile, by using the frequency discrimination method, phase noise performances of 5GHz radio frequency(RF) signals under different operating conditions were measured and the effective factors were studied. The experimental results demonstrate that oscillation mode depends on the cavity length of optical ring cavity. Optical signal polarization, phase matching and loop length have influence on the phase noise of the RF signals. The coupled optoelectronic oscillator of 5GHz RF signal and phase noises of -136dBc/Hz at 10kHz offset frequency is obtained, whose phase noise is the lowest in our country as far as we know.
2014, 38(5): 586-589.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.002
Abstract:
In order to realize omnidirectional detection and precise positioning of a target, a solution of the nonsymmetrical receiving optical system used for laser panoramic detection was presented based on imaging optics and non-imaging optics theory. Due to the significant difference between the meridianal and sagittal field, it was necessary to join the special asymmetric system to balance the big difference. Therefore the prism system and the inverted telescopic system were adopted to condense the field of sagittal direction. Then, the optical energy can be collected to the circular detector with a diameter of 1.5mm after the focusing system. The system was composed by an echelon prism, a aspheric lens, two cylindrical lens and two lenses, with the F-number of 0.56. The results show that a single set of system can complete the detection of ±30° field of view and six sets of receiving systems constitute a 360° field of view to complete panorama detection. This result is helpful for realizing no blind spot detection. The practical system has small volume, compact structure and good applicability.
In order to realize omnidirectional detection and precise positioning of a target, a solution of the nonsymmetrical receiving optical system used for laser panoramic detection was presented based on imaging optics and non-imaging optics theory. Due to the significant difference between the meridianal and sagittal field, it was necessary to join the special asymmetric system to balance the big difference. Therefore the prism system and the inverted telescopic system were adopted to condense the field of sagittal direction. Then, the optical energy can be collected to the circular detector with a diameter of 1.5mm after the focusing system. The system was composed by an echelon prism, a aspheric lens, two cylindrical lens and two lenses, with the F-number of 0.56. The results show that a single set of system can complete the detection of ±30° field of view and six sets of receiving systems constitute a 360° field of view to complete panorama detection. This result is helpful for realizing no blind spot detection. The practical system has small volume, compact structure and good applicability.
2014, 38(5): 590-594.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.003
Abstract:
In order to improve the conversion efficiency of the laser wireless power transmission system, based on the working principle of single junction GaAs photovoltaic cell, by the method of adjusting the parameter of laser which irradiated the photovoltaic cell, an optimization scheme was designed to each part of the laser wireless power transmission system theoretically. The relation between the conversion efficiency with laser wavelength and incident intensity was measured experimentally and discussed theoretically. The results show that the conversion efficiency of GaAs photovoltaic cell is improved obviously compared with monocrystalline silicon photovoltaic cell for monochromatic laser. The maximum conversion efficiency reaches 61.2%. The conclusions have a certain reference value for the application of laser wireless power transmission.
In order to improve the conversion efficiency of the laser wireless power transmission system, based on the working principle of single junction GaAs photovoltaic cell, by the method of adjusting the parameter of laser which irradiated the photovoltaic cell, an optimization scheme was designed to each part of the laser wireless power transmission system theoretically. The relation between the conversion efficiency with laser wavelength and incident intensity was measured experimentally and discussed theoretically. The results show that the conversion efficiency of GaAs photovoltaic cell is improved obviously compared with monocrystalline silicon photovoltaic cell for monochromatic laser. The maximum conversion efficiency reaches 61.2%. The conclusions have a certain reference value for the application of laser wireless power transmission.
2014, 38(5): 595-598.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.004
Abstract:
In order to study the propagation characteristics of Gaussian-Schell model(GSM) beams in negative index medium, the analytical expression was obtained for the cross-spectral density function of GSM beam passing through negative index medium based on the matrix optics theory, diffraction integral theory and unification theory of coherence and polarization. The spectral density and the spectral coherence degree of the beam passing through the negative index medium were obtained with the formula. Numerical examples show that both the spectral density and the coherence spectral degree of GSM beam can be modulated by the frequency of the negative index medium. The results provide a new modulation method for the beam propagation.
In order to study the propagation characteristics of Gaussian-Schell model(GSM) beams in negative index medium, the analytical expression was obtained for the cross-spectral density function of GSM beam passing through negative index medium based on the matrix optics theory, diffraction integral theory and unification theory of coherence and polarization. The spectral density and the spectral coherence degree of the beam passing through the negative index medium were obtained with the formula. Numerical examples show that both the spectral density and the coherence spectral degree of GSM beam can be modulated by the frequency of the negative index medium. The results provide a new modulation method for the beam propagation.
2014, 38(5): 599-602.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.005
Abstract:
In order to suppress the random signal fluctuations caused by the echo noise of Mie scattering atmospheric probe laser radar, a new adaptive segmentation smoothing method was designed to smooth the signal. According to the characteristics of lidar signal, the effective changing amplitude of the signal is greater than the change of background noise. The amplitude of the signal noise could be expressed by several times of the standard deviation of the background noise. After comparing the amplitude difference of the adjacent signal with the noise amplitude, the effective position of signal change was determined. These positions could be recorded as the segmental endpoints of the signal. The common moving average algorithm was applied to each segment of the lidar signal. The method was examined by using the actual micro pulse lidar signal and compared by the common fixed segment algorithm. The results show that the adaptive segment smoothing method can choose the size of the smoothing window automatically according the intensity of the signal change. The noise is suppressed effectively and the signal distortion caused by excessive smooth is avoided.
In order to suppress the random signal fluctuations caused by the echo noise of Mie scattering atmospheric probe laser radar, a new adaptive segmentation smoothing method was designed to smooth the signal. According to the characteristics of lidar signal, the effective changing amplitude of the signal is greater than the change of background noise. The amplitude of the signal noise could be expressed by several times of the standard deviation of the background noise. After comparing the amplitude difference of the adjacent signal with the noise amplitude, the effective position of signal change was determined. These positions could be recorded as the segmental endpoints of the signal. The common moving average algorithm was applied to each segment of the lidar signal. The method was examined by using the actual micro pulse lidar signal and compared by the common fixed segment algorithm. The results show that the adaptive segment smoothing method can choose the size of the smoothing window automatically according the intensity of the signal change. The noise is suppressed effectively and the signal distortion caused by excessive smooth is avoided.
2014, 38(5): 603-607.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.006
Abstract:
In order to get the integer pixel displacement information and the sub-pixel displacement information simultaneously at one time, the sub-pixel subarea was constructed by using the method of gray interpolation and the digital image correlation method based on particle swarm optimization algorithm was proposed. The applicability of the method was verified by measuring both the simulated speckle pattern with the translational information and with the strain information. And then, the integer pixel particle swarm algorithm and the sub-pixel of different magnitude interpolation gray particle swarm algorithm were compared by measuring the specimen with tiny rotational displacement. The results show that the particle swarm algorithm based on sub-pixel digital scattered spot image correlation method has advantages for small displacement measurement.
In order to get the integer pixel displacement information and the sub-pixel displacement information simultaneously at one time, the sub-pixel subarea was constructed by using the method of gray interpolation and the digital image correlation method based on particle swarm optimization algorithm was proposed. The applicability of the method was verified by measuring both the simulated speckle pattern with the translational information and with the strain information. And then, the integer pixel particle swarm algorithm and the sub-pixel of different magnitude interpolation gray particle swarm algorithm were compared by measuring the specimen with tiny rotational displacement. The results show that the particle swarm algorithm based on sub-pixel digital scattered spot image correlation method has advantages for small displacement measurement.
2014, 38(5): 608-613.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.007
Abstract:
In order to solve the problem of a traditional 5kW transverse CO2 laser with double discharge boxes, i.e., small wind entrance, low wind velocity and large size, a 5kW CO2 transverse laser with single discharge box was developed. Based on analysis of the flow field in the discharge area and gas dynamics, a lightweight aluminum centrifugal fan was designed on the premise of the same fan strength with entrance diameter of 382mm, outlet diameter of 451mm and volute width of 160mm. Then it was validated in experiments. The results show that, comparing with 5kW transverse laser with double discharge boxes, the power stability of 5kW CO2 transverse laser with single discharge box is improved. The average wind velocity of discharge area increases from 60.8m/s to 75.5m/s, the arc discharge area is reduced and the near-field intensity and uniformity is improved. The selection of lightweight aluminum fan and single discharge box decreases the weight and volume of the laser. The study is important and instructive for development of compact CO2 lasers with high power and small volume.
In order to solve the problem of a traditional 5kW transverse CO2 laser with double discharge boxes, i.e., small wind entrance, low wind velocity and large size, a 5kW CO2 transverse laser with single discharge box was developed. Based on analysis of the flow field in the discharge area and gas dynamics, a lightweight aluminum centrifugal fan was designed on the premise of the same fan strength with entrance diameter of 382mm, outlet diameter of 451mm and volute width of 160mm. Then it was validated in experiments. The results show that, comparing with 5kW transverse laser with double discharge boxes, the power stability of 5kW CO2 transverse laser with single discharge box is improved. The average wind velocity of discharge area increases from 60.8m/s to 75.5m/s, the arc discharge area is reduced and the near-field intensity and uniformity is improved. The selection of lightweight aluminum fan and single discharge box decreases the weight and volume of the laser. The study is important and instructive for development of compact CO2 lasers with high power and small volume.
2014, 38(5): 614-618.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.008
Abstract:
In order to solve the problem of high pump power of logic gates, a novel Mach-Zehnder type all optical logic gate based on micro-ring resonator was proposed. The periodical patterns of air holes added in the micro-ring waveguide provide strong confinement on light, which enhances the third order nonlinear Kerr effect around the band edge and decreases the pump power of phase shift. Combining micro-ring resonator with Mach-Zehnder structure, different logic function can be realized with the phase shift in the different micro-rings controlled by Kerr effect. The impact of the different size of air holes on the structure was calculated and the detailed control methods of the logic gates were verified. The feasibility was proved. The simulation results show that this device possesses several practical advantages, such as low power consumption of less than 10dBm, delay of ps order, high speed data processing ability and μm order dimension. The device achieves the different kinds of logic gates and has the guiding significance to all optical networks.
In order to solve the problem of high pump power of logic gates, a novel Mach-Zehnder type all optical logic gate based on micro-ring resonator was proposed. The periodical patterns of air holes added in the micro-ring waveguide provide strong confinement on light, which enhances the third order nonlinear Kerr effect around the band edge and decreases the pump power of phase shift. Combining micro-ring resonator with Mach-Zehnder structure, different logic function can be realized with the phase shift in the different micro-rings controlled by Kerr effect. The impact of the different size of air holes on the structure was calculated and the detailed control methods of the logic gates were verified. The feasibility was proved. The simulation results show that this device possesses several practical advantages, such as low power consumption of less than 10dBm, delay of ps order, high speed data processing ability and μm order dimension. The device achieves the different kinds of logic gates and has the guiding significance to all optical networks.
2014, 38(5): 619-622.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.009
Abstract:
In order to study the disturbing effect of pulsed laser against an array CCD, experiment of CCD imaging system disturbed by repeated pulse laser was carried out at short-distance. Crosstalk effect of the CCD was observed and recorded at an energy density of 2.97mJ/cm2 received by the CCD detector. When the electric shutter of the CCD vidicon was turned on, the images of excursion laser spots were found in the vertical direction of the laser radiation windows except for laser beam spot image. Operation principle of the electric shutter and the transfer mechanism of the CCD were analyzed. Phenomena of laser spot excursion were explained. Experimental results indicate that CCD images can be disturbed by the spot excursion caused by repeated pulse laser. The result lays the academic foundation and elementary experiment for CCD disturbed by repeated pulsed laser.
In order to study the disturbing effect of pulsed laser against an array CCD, experiment of CCD imaging system disturbed by repeated pulse laser was carried out at short-distance. Crosstalk effect of the CCD was observed and recorded at an energy density of 2.97mJ/cm2 received by the CCD detector. When the electric shutter of the CCD vidicon was turned on, the images of excursion laser spots were found in the vertical direction of the laser radiation windows except for laser beam spot image. Operation principle of the electric shutter and the transfer mechanism of the CCD were analyzed. Phenomena of laser spot excursion were explained. Experimental results indicate that CCD images can be disturbed by the spot excursion caused by repeated pulse laser. The result lays the academic foundation and elementary experiment for CCD disturbed by repeated pulsed laser.
2014, 38(5): 623-626.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.010
Abstract:
In order to achieve rapid and accurate measurement of sphere bearing ball during manufacturing process, a set of Michelson interferometer measurement system was proposed based on white light interferometer technology, image processing technology and signal processing technology. White light interferometry technique was analyzed theoretically. The precision and roughness measurement of the optical spherical radius of sphere ball bearing were made. The finish resolution image and the curvature radius image were obtained. The accurate calculation data was obtained after processing a large number of experimental data. The finish resolution can reach the nm level and the curvature can be calculated to the μm level. The processing quality and the detection speed are improved.
In order to achieve rapid and accurate measurement of sphere bearing ball during manufacturing process, a set of Michelson interferometer measurement system was proposed based on white light interferometer technology, image processing technology and signal processing technology. White light interferometry technique was analyzed theoretically. The precision and roughness measurement of the optical spherical radius of sphere ball bearing were made. The finish resolution image and the curvature radius image were obtained. The accurate calculation data was obtained after processing a large number of experimental data. The finish resolution can reach the nm level and the curvature can be calculated to the μm level. The processing quality and the detection speed are improved.
2014, 38(5): 627-631.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.011
Abstract:
In order to study the local deformation field of crack tip and fracture characteristics in fracture mechanics, static fracture tests of the limited-width polymethyl methacrylate specimen with center-crack were carried out with digital gradient sensing method. Speckle patterns under different states of stress near the crack tip were recorded by CCD in the experiment. Angular deflection was obtained by digital image correlation method and stress intensity factor in mode Ⅰ crack was extracted by angular deflection. It shows that the stress intensity factor calculated by digital gradient sensing measurement method is consistent with theoretical results.
In order to study the local deformation field of crack tip and fracture characteristics in fracture mechanics, static fracture tests of the limited-width polymethyl methacrylate specimen with center-crack were carried out with digital gradient sensing method. Speckle patterns under different states of stress near the crack tip were recorded by CCD in the experiment. Angular deflection was obtained by digital image correlation method and stress intensity factor in mode Ⅰ crack was extracted by angular deflection. It shows that the stress intensity factor calculated by digital gradient sensing measurement method is consistent with theoretical results.
2014, 38(5): 632-637.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.012
Abstract:
To improve the yield rate and scribing efficiency of sapphire substrate, the effect of polarization direction, laser power, focus position, cutting speed, scanning times on the scribing quality of sapphire substrate with pulse green laser (λ=532nm) was studied.The results show that narrow and deep grooves can be obtained when the polarization direction is parallel to the incidence plane and the laser focus position is negative defocus 50μm when scribing sapphire substrate with pulse green laser. The groove depth and width increase while the pulse laser power increases. The groove depth decreases and the groove width increases at first and then decreases with the increase of the scanning speed. The groove depth and width increase with the increase of the scanning times. The results are helpful for selection of reasonable laser scribing technical parameters to achieve optimal groove performance.
To improve the yield rate and scribing efficiency of sapphire substrate, the effect of polarization direction, laser power, focus position, cutting speed, scanning times on the scribing quality of sapphire substrate with pulse green laser (λ=532nm) was studied.The results show that narrow and deep grooves can be obtained when the polarization direction is parallel to the incidence plane and the laser focus position is negative defocus 50μm when scribing sapphire substrate with pulse green laser. The groove depth and width increase while the pulse laser power increases. The groove depth decreases and the groove width increases at first and then decreases with the increase of the scanning speed. The groove depth and width increase with the increase of the scanning times. The results are helpful for selection of reasonable laser scribing technical parameters to achieve optimal groove performance.
2014, 38(5): 638-642.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.013
Abstract:
In order to improve the accuracy of a phase-shift range finder, a phase-difference algorithm based on phase-shift correlation analysis was proposed to estimate the phase-difference between two sinusoidal signals with same frequency. For reducing the influence of noise, the autocorrelation between the original and 2π shifted signal was calculated firstly. Secondly, the phase difference was estimated approximately with a few sampled data and the initial phase of one signal was shifted by Δθ to make the phase difference between two signals to be near π/2(or 3π/2). Then, the phase-difference was calculated with whole set of data by correlation method and the final phase difference was obtained by subtracting Δθ. The influence of frequency error was analyzed. Theoretical analysis and simulation shows that the error of this method is greatly reduced. The proposed method can improve the accuracy of a range finder.
In order to improve the accuracy of a phase-shift range finder, a phase-difference algorithm based on phase-shift correlation analysis was proposed to estimate the phase-difference between two sinusoidal signals with same frequency. For reducing the influence of noise, the autocorrelation between the original and 2π shifted signal was calculated firstly. Secondly, the phase difference was estimated approximately with a few sampled data and the initial phase of one signal was shifted by Δθ to make the phase difference between two signals to be near π/2(or 3π/2). Then, the phase-difference was calculated with whole set of data by correlation method and the final phase difference was obtained by subtracting Δθ. The influence of frequency error was analyzed. Theoretical analysis and simulation shows that the error of this method is greatly reduced. The proposed method can improve the accuracy of a range finder.
2014, 38(5): 643-646.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.014
Abstract:
In order to improve the compression ratio of the hyperspectral remote sensing images, a new lookup table(LUT) prediction method was proposed based on residual offset. In the first spectral band of the hyperspectral images, the prediction was conducted within the spectral band by the median prediction method of lossless compression standard. In other spectral bands, the prediction was conducted between the spectral bands. Firstly, the current prediction value was found through locally averaged interband scaling lookup table (LAIS-LUT) prediction method. Then, the specific five pixels around the current prediction value were compared with the corresponding five pixels around the current value. After the comparison, the offset was obtained. The offset was added to the prediction residual error. Finally, the prediction residual error will be coded with algorithm coding. Theoretical analysis and experimental verification show that the lossless compression ratio of the proposed method is increased by about 0.05 in National Aeronautics and Space Administration data and by about 0.07 in Chinese data. This result is helpful to improve the compression efficiency of hyperspectral images.
In order to improve the compression ratio of the hyperspectral remote sensing images, a new lookup table(LUT) prediction method was proposed based on residual offset. In the first spectral band of the hyperspectral images, the prediction was conducted within the spectral band by the median prediction method of lossless compression standard. In other spectral bands, the prediction was conducted between the spectral bands. Firstly, the current prediction value was found through locally averaged interband scaling lookup table (LAIS-LUT) prediction method. Then, the specific five pixels around the current prediction value were compared with the corresponding five pixels around the current value. After the comparison, the offset was obtained. The offset was added to the prediction residual error. Finally, the prediction residual error will be coded with algorithm coding. Theoretical analysis and experimental verification show that the lossless compression ratio of the proposed method is increased by about 0.05 in National Aeronautics and Space Administration data and by about 0.07 in Chinese data. This result is helpful to improve the compression efficiency of hyperspectral images.
2014, 38(5): 647-650.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.015
Abstract:
To improve the suppression capability of the background stray light and the small-target detection capability of a laser rangefinder, a field diaphragm matching with the field was added in the receiving optical system of the laser rangefinder. Good results were obtained by the theoretical analysis and the experimental verification. The results show that the field diaphragm has better effect on the stray light suppression, the noise reduction and the detection sensitivity improvement. The ability of laser rangefinder with the field diaphragm was improved to about 1.18 times than that without the field diaphragm. The new laser rangefinder has better ranging capability than before.
To improve the suppression capability of the background stray light and the small-target detection capability of a laser rangefinder, a field diaphragm matching with the field was added in the receiving optical system of the laser rangefinder. Good results were obtained by the theoretical analysis and the experimental verification. The results show that the field diaphragm has better effect on the stray light suppression, the noise reduction and the detection sensitivity improvement. The ability of laser rangefinder with the field diaphragm was improved to about 1.18 times than that without the field diaphragm. The new laser rangefinder has better ranging capability than before.
2014, 38(5): 651-654.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.016
Abstract:
In order to overcome the disadvantages of the traditional head detection, such as limited size of measuring models, low accuracy of artificial reading and resource cost of plate making, a non-contact laser detection device, suitable for shape deviation detection of the head in different sizes, was designed with laser scanning 2-D contour continuously. Work principle, scan mode, system components and specific design of each subsystem of the laser scanning head device were introduced. A head with inner diameter of 800mm was verified in experiment. The results show that the laser scanning head device can make the detection automatically with high-precision, high-efficiency. The ideal accuracy can reach 1mm~2mm.
In order to overcome the disadvantages of the traditional head detection, such as limited size of measuring models, low accuracy of artificial reading and resource cost of plate making, a non-contact laser detection device, suitable for shape deviation detection of the head in different sizes, was designed with laser scanning 2-D contour continuously. Work principle, scan mode, system components and specific design of each subsystem of the laser scanning head device were introduced. A head with inner diameter of 800mm was verified in experiment. The results show that the laser scanning head device can make the detection automatically with high-precision, high-efficiency. The ideal accuracy can reach 1mm~2mm.
2014, 38(5): 655-659.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.017
Abstract:
In order to adjust the size of bottle beam which was not adjustable flexibly in a current optical system, a novel optical system composed of one frustum and one axicon with different conical angle was proposed. The beam transformation property of this new system was analyzed by diffraction integral and Hankel wave theory. When a plane wave passes through the novel optical system, a bottle beam is formed and the size of bottle beam can be adjusted by changing the relative position between both the optical elements. Based on the analysis, the relevant parameters of bottle beam were also calculated by geometrical optics. The intensity distribution of bottle beam in different positions after the novel optical system was simulated by TRACEPRO software and the intensity distribution with the change of the relative position between frustum and axicon was also analyzed. The result of simulation is consistent with the result of theoretical analysis. The conclusion shows that bottle beam with adjustable size can be generated by the novel optical system.
In order to adjust the size of bottle beam which was not adjustable flexibly in a current optical system, a novel optical system composed of one frustum and one axicon with different conical angle was proposed. The beam transformation property of this new system was analyzed by diffraction integral and Hankel wave theory. When a plane wave passes through the novel optical system, a bottle beam is formed and the size of bottle beam can be adjusted by changing the relative position between both the optical elements. Based on the analysis, the relevant parameters of bottle beam were also calculated by geometrical optics. The intensity distribution of bottle beam in different positions after the novel optical system was simulated by TRACEPRO software and the intensity distribution with the change of the relative position between frustum and axicon was also analyzed. The result of simulation is consistent with the result of theoretical analysis. The conclusion shows that bottle beam with adjustable size can be generated by the novel optical system.
2014, 38(5): 660-664.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.018
Abstract:
In order to prove that the microwave photonic frequency multiplication system can be one part of radio over fiber transmission system, the microwave photonic system based on polarization modulator with the adjustable frequency multiplication factors and without the effect of fiber dispersion was demonstrated. The system principles and characteristics of two, four and six frequency multiplication based on the polarization modulator were analyzed theoretically. The responding different schemes were designed for different frequency multiplication factors. The experimental demonstration, data analysis and experimental result discussion were carried out. The good output of frequency multiplication was achieved on the basis of the ongoing optimization of the experimental system. The results show that the frequency multiplication output of the microwave/millimeter wave signals can be up to 42GHz within the scope of the instrument allowed. The system has the advantage of the small effect of fiber dispersion.
In order to prove that the microwave photonic frequency multiplication system can be one part of radio over fiber transmission system, the microwave photonic system based on polarization modulator with the adjustable frequency multiplication factors and without the effect of fiber dispersion was demonstrated. The system principles and characteristics of two, four and six frequency multiplication based on the polarization modulator were analyzed theoretically. The responding different schemes were designed for different frequency multiplication factors. The experimental demonstration, data analysis and experimental result discussion were carried out. The good output of frequency multiplication was achieved on the basis of the ongoing optimization of the experimental system. The results show that the frequency multiplication output of the microwave/millimeter wave signals can be up to 42GHz within the scope of the instrument allowed. The system has the advantage of the small effect of fiber dispersion.
2014, 38(5): 665-668.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.019
Abstract:
In order to stabilize the output frequency of 1064nm single frequency fiber laser, the Pound-Drever-Hall(PDH) locking technique was applied for laser frequency stabilization. The PDH optical heterodyne frequency stabilization system was established. The phase modulation optical heterodyne signal and the demodulation error signal were analyzed. Field-programmable gate array(FPGA) based digital PDH demodulation and feedback control system was designed. A sine wave generator and the multiplication demodulation were implemented in FPGA. Then the error signals were obtained by digital/analog convector. Experimental results show that phase modulation optical heterodyne signal is demodulated successfully in FPGA, and the Allan variance of frequency drifts can reach 10-11, a high level of frequency stabilization.
In order to stabilize the output frequency of 1064nm single frequency fiber laser, the Pound-Drever-Hall(PDH) locking technique was applied for laser frequency stabilization. The PDH optical heterodyne frequency stabilization system was established. The phase modulation optical heterodyne signal and the demodulation error signal were analyzed. Field-programmable gate array(FPGA) based digital PDH demodulation and feedback control system was designed. A sine wave generator and the multiplication demodulation were implemented in FPGA. Then the error signals were obtained by digital/analog convector. Experimental results show that phase modulation optical heterodyne signal is demodulated successfully in FPGA, and the Allan variance of frequency drifts can reach 10-11, a high level of frequency stabilization.
2014, 38(5): 669-674.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.020
Abstract:
In order to maintain the stability of the emission wavelength of an optical transceiver, a thermoelectric cooler was adopted to control the temperature in the transceiver. A temperature control circuit was designed with high sampling precision and fast response speed. Through theoretical analysis and experimental verification, the dependence of emission wavelength on the temperature was obtained in the application temperature range. The results show that the optimized temperature control circuit of thermoelectric cooler has good performance, which can control the temperature of the laser accurately and quickly and lock the emission wavelength within 20pm change range. The design meets the requirements of practical applications fully.
In order to maintain the stability of the emission wavelength of an optical transceiver, a thermoelectric cooler was adopted to control the temperature in the transceiver. A temperature control circuit was designed with high sampling precision and fast response speed. Through theoretical analysis and experimental verification, the dependence of emission wavelength on the temperature was obtained in the application temperature range. The results show that the optimized temperature control circuit of thermoelectric cooler has good performance, which can control the temperature of the laser accurately and quickly and lock the emission wavelength within 20pm change range. The design meets the requirements of practical applications fully.
2014, 38(5): 675-678.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.021
Abstract:
Because of the large thickness and low thermal conductivity of GaAs substrate in external-cavity surface-emitting laser, the heat diffusion of active region is seriously impeded and the laser output power is difficult to improve. In order to remove the GaAs substrate, sulfate acid corrosion was used. The corrosion effects were compared with different concentration etching liquid at different temperature. Atomic force microscope photos were used to represent the roughness of etching surface. The results show that when the volume ratio of the etching liquid V(H2SO4)：V(H2O2)：V(H2O) is 1：5：10 and the temperature is 30℃, the moderate etching rate about 5.2μm/min and the 2.7nm roughness of etching surface is obtained. The good etching effect of GaAs substrate provides the basic guarantee for the next step of the substrate removal-selective etch of the stop-layer.
Because of the large thickness and low thermal conductivity of GaAs substrate in external-cavity surface-emitting laser, the heat diffusion of active region is seriously impeded and the laser output power is difficult to improve. In order to remove the GaAs substrate, sulfate acid corrosion was used. The corrosion effects were compared with different concentration etching liquid at different temperature. Atomic force microscope photos were used to represent the roughness of etching surface. The results show that when the volume ratio of the etching liquid V(H2SO4)：V(H2O2)：V(H2O) is 1：5：10 and the temperature is 30℃, the moderate etching rate about 5.2μm/min and the 2.7nm roughness of etching surface is obtained. The good etching effect of GaAs substrate provides the basic guarantee for the next step of the substrate removal-selective etch of the stop-layer.
2014, 38(5): 679-683.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.022
Abstract:
Because of the actual situation of the lack of ultrahigh-speed pulser for Brillouin sensor technique, the design method of an ultrahigh-speed pulser was introduced based on field-programmable gate array (FPGA) device. In order to achieve smaller inter-symbol interference and better signal integrity, the crosstalk, modeling and electro-magnetic field of sensitive signal were analyzed. The time-domain waveforms and eye diagrams of the pulse with different pulse width were measured with a broadband oscilloscope. The generated pulse was specified by the minimum pulse width of 1ns, the maximum swing of 1.0V and the rising and falling transition time of less than 300ps. The pulse width could range from 1ns to 5ns, while repetitive frequency could range from 1kHz to 10kHz. This result is helpful for improving the design of ultrahigh-speed pulsers.
Because of the actual situation of the lack of ultrahigh-speed pulser for Brillouin sensor technique, the design method of an ultrahigh-speed pulser was introduced based on field-programmable gate array (FPGA) device. In order to achieve smaller inter-symbol interference and better signal integrity, the crosstalk, modeling and electro-magnetic field of sensitive signal were analyzed. The time-domain waveforms and eye diagrams of the pulse with different pulse width were measured with a broadband oscilloscope. The generated pulse was specified by the minimum pulse width of 1ns, the maximum swing of 1.0V and the rising and falling transition time of less than 300ps. The pulse width could range from 1ns to 5ns, while repetitive frequency could range from 1kHz to 10kHz. This result is helpful for improving the design of ultrahigh-speed pulsers.
2014, 38(5): 684-687.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.023
Abstract:
In order to analyze effect of different power laser on the temperature fields of the metal/explosive structure and the possibility of thermal explosion of the explosive, the three-dimensional temperature field of the metal/explosive structure irradiated by 55kW, 60kW, 65kW continuous laser was calculated based on a finite element analysis software, ANSYS. In the numerical model, the variation of the physical parameters of the metal materials and the surface energy coupling coefficient of steel target with the change of the temperature was also taken into account. The temperature distribution of the facular center axis direction and the temperature variation curve of the explosive and metal surface center with the change of irradiation time, were given. Under 5s of laser irradiation with different power, i.e., 55kW, 60kW and 65kW, the surface temperatures of the explosive were 521K,550K and 581K respectively. The greater the laser power, the higher the temperature and the easier the explosion. The temperature rise of the explosive is different when the power increases at different time. The temperature rise of the explosive occurs in a small area in contact with the metal within a certain irradiation time. These results have guiding significance to further study on metal/explosive irradiated by laser.
In order to analyze effect of different power laser on the temperature fields of the metal/explosive structure and the possibility of thermal explosion of the explosive, the three-dimensional temperature field of the metal/explosive structure irradiated by 55kW, 60kW, 65kW continuous laser was calculated based on a finite element analysis software, ANSYS. In the numerical model, the variation of the physical parameters of the metal materials and the surface energy coupling coefficient of steel target with the change of the temperature was also taken into account. The temperature distribution of the facular center axis direction and the temperature variation curve of the explosive and metal surface center with the change of irradiation time, were given. Under 5s of laser irradiation with different power, i.e., 55kW, 60kW and 65kW, the surface temperatures of the explosive were 521K,550K and 581K respectively. The greater the laser power, the higher the temperature and the easier the explosion. The temperature rise of the explosive is different when the power increases at different time. The temperature rise of the explosive occurs in a small area in contact with the metal within a certain irradiation time. These results have guiding significance to further study on metal/explosive irradiated by laser.
2014, 38(5): 688-691.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.024
Abstract:
In order to study effect of Compton scattering on the radiation damping effects in ultra-intense laser plasma, the effect of plasma induced by different polarized lasers was analyzed and calculated based on the model of multi-photon nonlinear Compton scattering, relativity theory and Lorentz transformation. The new mechanism of the radiation damping effect induced by Compton scattering in plasma was presented and the revised equation on the radiation damping effect was put forward. The results show that the probability of electron movement is increased because the required incident laser intensity is reduced and then the electron frequency and the coupling frequency of the electric field are increased. The multi-photon nonlinear Compton scattering is an important mechanism on taking and increasing the radiation damping effect of plasma.
In order to study effect of Compton scattering on the radiation damping effects in ultra-intense laser plasma, the effect of plasma induced by different polarized lasers was analyzed and calculated based on the model of multi-photon nonlinear Compton scattering, relativity theory and Lorentz transformation. The new mechanism of the radiation damping effect induced by Compton scattering in plasma was presented and the revised equation on the radiation damping effect was put forward. The results show that the probability of electron movement is increased because the required incident laser intensity is reduced and then the electron frequency and the coupling frequency of the electric field are increased. The multi-photon nonlinear Compton scattering is an important mechanism on taking and increasing the radiation damping effect of plasma.
2014, 38(5): 692-697.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.025
Abstract:
In order to improve the working speed of adaptive optics as soon as possible, the algorithm of automatic control theory was applied for adaptive optical system without changing the characteristics of the hardware. After analyzing the close-loop control system of the adaptive optical system, the mathematical model of adaptive optical control was constructed. The controllers and the control algorithms were designed and their characteristics were discussed based on the automatic control theory. After combining the automatic control algorithms and human eye wave-front aberration correction, the control algorithm was applied to the aberration correction. The experiment result shows that the Smith estimating precompensation control has higher closed-loop bandwidth, better dynamic and steady state characteristics than proportion-integration (PI) control and integrator control. The result of the Smith estimating precompensation control has better speed in static aberration correction of the bogus mode eye and makes the root mean square least in the dynamic aberration correction of human eye. So the Smith estimating precompensation control can optimize the control system of adaptive optics.
In order to improve the working speed of adaptive optics as soon as possible, the algorithm of automatic control theory was applied for adaptive optical system without changing the characteristics of the hardware. After analyzing the close-loop control system of the adaptive optical system, the mathematical model of adaptive optical control was constructed. The controllers and the control algorithms were designed and their characteristics were discussed based on the automatic control theory. After combining the automatic control algorithms and human eye wave-front aberration correction, the control algorithm was applied to the aberration correction. The experiment result shows that the Smith estimating precompensation control has higher closed-loop bandwidth, better dynamic and steady state characteristics than proportion-integration (PI) control and integrator control. The result of the Smith estimating precompensation control has better speed in static aberration correction of the bogus mode eye and makes the root mean square least in the dynamic aberration correction of human eye. So the Smith estimating precompensation control can optimize the control system of adaptive optics.
2014, 38(5): 698-702.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.026
Abstract:
In order to overcome the channel fade effect caused by the atmospheric turbulence, the free space optical (FSO) system model with spatial diversity was analyzed based on intensity detection pulse position modulation (PPM) in weak turbulence atmosphere. The calculating formula of slot error rate (SER) of the system without diversity was derived under PPM firstly. Then as a benchmark, under the case of independent and identical distribution, the average slot error rates of three linear combining technologies, i.e., the maximal ratio combing (MRC), equal gain combining (EGC) and selection combining (SC) were compared by means of numerical simulation. The results show that the improvement of system by MRC is the best, followed by EGC and SC is poor. However, SC is simpler and more convenient. The technology of spatial diversity receiver combination is efficient to improve the performance of FSO and has strong ability of resistance to atmospheric channel fade, and is suited for optical wireless communications systems.
In order to overcome the channel fade effect caused by the atmospheric turbulence, the free space optical (FSO) system model with spatial diversity was analyzed based on intensity detection pulse position modulation (PPM) in weak turbulence atmosphere. The calculating formula of slot error rate (SER) of the system without diversity was derived under PPM firstly. Then as a benchmark, under the case of independent and identical distribution, the average slot error rates of three linear combining technologies, i.e., the maximal ratio combing (MRC), equal gain combining (EGC) and selection combining (SC) were compared by means of numerical simulation. The results show that the improvement of system by MRC is the best, followed by EGC and SC is poor. However, SC is simpler and more convenient. The technology of spatial diversity receiver combination is efficient to improve the performance of FSO and has strong ability of resistance to atmospheric channel fade, and is suited for optical wireless communications systems.
2014, 38(5): 703-708.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.027
Abstract:
In order to solve the nonparaxial vector wave equation in the cylindrical coordinates and obtain electric field expression of the beams, based on the electric field along the azimuthal polarization under the axisymmetric circumstance, the vector wave equation under the nonparaxiality similar circumstances was transformed to the parabolic coordinates and was solved appropriately with the separation variables method. The corresponding numerical calculation was made. The results show that the new analytical solution of the nonparaxial vector wave equation is discussed to describe the propagation of a laser beam. The electric field of such a beam is found to be based on the solutions of the confluent hypergeometric function and the Meijer functions. The intensity distribution of beam is similar to the first-class zero-order Bessel beam mode. The intensity of the light beam near the optical axis is nearly infinite, and decays rapidly along the peripheral direction and decreases sharply along the radial direction in the focal plane. The acquired results are of certain significance for exploring the propagation properties of vector beams in case of nonparaxial approximation.
In order to solve the nonparaxial vector wave equation in the cylindrical coordinates and obtain electric field expression of the beams, based on the electric field along the azimuthal polarization under the axisymmetric circumstance, the vector wave equation under the nonparaxiality similar circumstances was transformed to the parabolic coordinates and was solved appropriately with the separation variables method. The corresponding numerical calculation was made. The results show that the new analytical solution of the nonparaxial vector wave equation is discussed to describe the propagation of a laser beam. The electric field of such a beam is found to be based on the solutions of the confluent hypergeometric function and the Meijer functions. The intensity distribution of beam is similar to the first-class zero-order Bessel beam mode. The intensity of the light beam near the optical axis is nearly infinite, and decays rapidly along the peripheral direction and decreases sharply along the radial direction in the focal plane. The acquired results are of certain significance for exploring the propagation properties of vector beams in case of nonparaxial approximation.
2014, 38(5): 709-712.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.028
Abstract:
To reduce the calculation error induced by the uncertainty of the parameters, such as spectrum spontaneous emission transition probabilities, the electron temperature of the laser-induced water scale plasma was studied using a modified iterative Boltzmann algorithm. After 12 iterations, the linear correlation coefficient was increased from 0.7687 up to 0.99991 while the electron temperature of the water scale plasma was 5012K. After the fitting of Ca Ⅱ 393.37nm by Lorentz function, the electron density of water scale plasma was 5.7×1016cm-3, much higher than the critical value of 6.4×1015cm-3. The laser-induced water scale plasma was proved to meet the local thermodynamic equilibrium model. The experimental results show that this method not only is simple, but also can improve the solution accuracy of the characteristic parameters of the plasma significantly.
To reduce the calculation error induced by the uncertainty of the parameters, such as spectrum spontaneous emission transition probabilities, the electron temperature of the laser-induced water scale plasma was studied using a modified iterative Boltzmann algorithm. After 12 iterations, the linear correlation coefficient was increased from 0.7687 up to 0.99991 while the electron temperature of the water scale plasma was 5012K. After the fitting of Ca Ⅱ 393.37nm by Lorentz function, the electron density of water scale plasma was 5.7×1016cm-3, much higher than the critical value of 6.4×1015cm-3. The laser-induced water scale plasma was proved to meet the local thermodynamic equilibrium model. The experimental results show that this method not only is simple, but also can improve the solution accuracy of the characteristic parameters of the plasma significantly.
2014, 38(5): 713-717.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.029
Abstract:
In order to gain better segmentation result of infrared images, and improve the ability to resist noise, an improved 2-D Otsu method was proposed. The inaccurate segmentation in the 2-D gray-neighborhood average histogram was analyzed, and 2-D gray-gradient histogram was adopted. A new algorithm to gain neighborhood average value was put forward. Information of within-cluster was added to amend threshold function, which was further simplified to reduce the calculation complex. Experiments show that the improved method can segment the target better, gain better noise resistance and cost less time.
In order to gain better segmentation result of infrared images, and improve the ability to resist noise, an improved 2-D Otsu method was proposed. The inaccurate segmentation in the 2-D gray-neighborhood average histogram was analyzed, and 2-D gray-gradient histogram was adopted. A new algorithm to gain neighborhood average value was put forward. Information of within-cluster was added to amend threshold function, which was further simplified to reduce the calculation complex. Experiments show that the improved method can segment the target better, gain better noise resistance and cost less time.
2014, 38(5): 718-722.
doi: 10.7510/jgjs.issn.1001-3806.2014.05.030
Abstract:
In order to study the field distribution of 1-D photonic crystal, the formula of the light intensity distribution of TM wave in 1-D photonic crystal was deduced based on the characteristic matrix and the intensity of TM wave and TE wave in 1-D photonic crystal was analyzed. The results show that the light intensity of TM wave and TE wave decreases with the increase of propagation depth in forbidden band of 1-D photonic crystal. The light intensity of TM wave and TE wave does not decrease with the increase of propagation depth in conductive band of 1-D photonic crystal. The study is helpful for the understanding of forbidden band and conductive band in TM wave and TE wave.
In order to study the field distribution of 1-D photonic crystal, the formula of the light intensity distribution of TM wave in 1-D photonic crystal was deduced based on the characteristic matrix and the intensity of TM wave and TE wave in 1-D photonic crystal was analyzed. The results show that the light intensity of TM wave and TE wave decreases with the increase of propagation depth in forbidden band of 1-D photonic crystal. The light intensity of TM wave and TE wave does not decrease with the increase of propagation depth in conductive band of 1-D photonic crystal. The study is helpful for the understanding of forbidden band and conductive band in TM wave and TE wave.
